JP2014207753A - Electronic equipment, motor drive device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to insert and withdraw live wire on a circuit board safely with an inexpensive configuration.SOLUTION: A motor driver 203 to be a high voltage source is connected to a ground line 302 via a motor 303. A low voltage source 301 is connected to the ground line 302 via an encoder sensor circuit 304. A current limit resistor 305 is connected in series to a line connecting an output terminal 301a of the low voltage source 301 and an input terminal 304a of the encoder sensor circuit 304 to form a motor module. Thus, in inserting and withdrawing live wire of the motor module, the amount of a current reversely flowing into the encoder sensor circuit 304 from the motor driver 203 through the ground line 302 can be significantly reduced, and thereby inconvenience is prevented in which the encoder sensor circuit 304 is damaged by the reversely flowing current. The above configuration requires only the connection of the current limit resistor 305 and can be implemented at a low cost.

Description

  The present invention relates to an electronic device, a motor drive device, and an image forming apparatus.

  Electronic devices today are often inserted into and removed from a backboard (busbar) in units of modular circuit boards. However, if the circuit board is inserted into and removed from the backboard without grounding the circuit board with respect to the ground, the current that should have been grounded will flow through the inflow path different from the original inflow path. Flow and circuit may be damaged.

  For example, in the case of a circuit board of a motor module, a motor driver that drives the motor and an encoder sensor circuit that detects the rotational position of the motor are installed on the same circuit board and modularized. The motor driver and encoder sensor circuit are connected to a common ground line on the circuit board. The motor driver is driven with a voltage of 24V, for example, and the encoder sensor circuit is driven with a voltage of 5V, for example.

  If such a motor module is inserted into or removed from the backboard while the ground line is not grounded, the current for driving the motor driver flows back into the encoder sensor circuit via the ground line. Cause inconvenience. This reverse flow of current causes a potential difference of 19V in the encoder sensor circuit, which causes a problem that the encoder sensor circuit is damaged.

  In Patent Document 1 (Japanese Patent Laid-Open No. Hei 6-168863), when a circuit board is hot-plugged with respect to a backboard (busbar), fluctuations in the power busbar or signal busbar are reduced and the influence on other circuit boards is affected. A hot-wire insertion / extraction system aimed at preventing the above has been disclosed.

  In this hot-swap method, a voltage dividing adjustment circuit is formed using a resistor and a Zener diode. When the circuit board is disconnected from the external interface and reconnected, the occurrence of inrush current in a transient state at the time of insertion / extraction is limited by voltage division adjustment by the voltage division adjustment circuit. Thereby, the charging / discharging current generated at the time of hot-line insertion can be suppressed, and the hot-swap of the circuit board can be performed without adversely affecting other circuit boards.

  However, the hot-swap method disclosed in Patent Document 1 uses a Zener diode to form a voltage dividing adjustment circuit. Zener diodes are expensive parts. For this reason, if voltage dividing circuits formed using Zener diodes are provided on a large number of circuit boards that are modularized, there is a problem that the cost of the entire apparatus increases.

  SUMMARY An advantage of some aspects of the invention is that it provides an electronic device, a motor drive device, and an image forming apparatus that enable hot-line insertion / extraction of a circuit board safely with an inexpensive configuration.

  In order to solve the above-described problems and achieve the object, the present invention provides a power supply unit including at least a first power supply unit and a second power supply unit that supplies a lower voltage than the first power supply unit. A drive unit including at least a first drive unit driven by a voltage from the first power supply unit, and a second drive unit driven by a voltage from the second power supply unit, and a drive unit And a resistor connected in series to a line connecting the second power supply unit and the second drive unit.

  According to the present invention, there is an effect that it is possible to safely perform hot-line insertion / extraction of a circuit board with an inexpensive configuration.

FIG. 1 is a mechanical configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a schematic electrical system diagram of the image forming apparatus according to the embodiment. FIG. 3 is a circuit configuration diagram of a motor module that rotationally drives the paper feed roller. FIG. 4 is a circuit diagram of an incremental encoder sensor circuit that outputs a two-phase encoded output provided in the image forming apparatus according to the embodiment. FIG. 5 is a diagram illustrating a relationship between the photodetector of the encoder sensor circuit provided in the image forming apparatus according to the embodiment and the slit of the code disk. FIG. 6 is a diagram illustrating a two-phase encoding output output from an encoder sensor circuit provided in the image forming apparatus according to the embodiment. FIG. 7 is a circuit configuration diagram of a motor module as a comparative example. FIG. 8 is a diagram illustrating a current path and a current amount when the motor module provided in the image forming apparatus according to the embodiment is hot-plugged. FIG. 9 is a circuit diagram of an incremental encoder sensor circuit that outputs a one-phase encoded output. FIG. 10 is a diagram illustrating a main part of an image forming apparatus which is a modification of the embodiment in which a Hall element sensor is provided instead of the two-phase encoder sensor circuit.

  Exemplary embodiments of an electronic device, a motor driving device, and an image forming apparatus will be described below in detail with reference to the accompanying drawings.

(Embodiment)
FIG. 1 is a mechanical configuration diagram illustrating an example of an image forming apparatus 100 according to the present embodiment. An image forming apparatus 100 illustrated in FIG. 1 is a so-called tandem type image forming apparatus, and has a configuration in which AIO cartridges 6Bk, 6M, 6C, and 6Y for each color are arranged along a transfer belt 5. The transfer belt 5 rotates counterclockwise on the paper surface of FIG. On the transfer belt 5, AIO cartridges 6Bk, 6M, 6C, and 6Y are sequentially arranged from the upstream side in the rotation direction. Each AIO cartridge 6Bk, 6M, 6C, 6Y has the same internal configuration except that the color of the image to be formed is different. The AIO cartridge 6Bk forms a black image, the AIO cartridge 6M forms a magenta image, the AIO cartridge 6C forms a cyan image, and the AIO cartridge 6Y forms a yellow image.

  Hereinafter, the description will be given by taking the AIO cartridge 6Bk as an example, but the configurations of the other AIO cartridges 6M, 6C, and 6Y are the same as the configuration of the AIO cartridge 6Bk. For this reason, the constituent elements of the AIO cartridges 6M, 6C, and 6Y will be described with reference to the figures distinguished by M, C, and Y instead of the Bk attached to the constituent elements of the AIO cartridge 6Bk. Is omitted.

  The transfer belt 5 is an endless belt wound around a secondary transfer drive roller 7 and a transfer belt tension roller 8 that are rotationally driven. The secondary transfer drive roller 7 is rotationally driven by a drive motor (not shown).

  The AIO cartridge 6Bk includes a photoconductor 9Bk, a charger 10Bk disposed around the photoconductor 9Bk, an exposure device 11, a developing device 12Bk, a cleaner blade 13Bk, and the like. The exposure device 11 includes an exposure device 11Bk for black images, an exposure device 11C for cyan images, an exposure device 11M for magenta images, and an exposure device 11Y for yellow images. That is, the image forming apparatus 100 is provided with the same number of exposure devices 11Bk, 11C, 11M, and 11Y as the number of toner colors. The exposure apparatus 11 is configured to irradiate laser beams 14Bk, 14M, 14C, and 14Y that are examples of exposure light corresponding to image colors formed by the AIO cartridges 6Bk, 6M, 6C, and 6Y.

  At the time of image formation, the outer peripheral surface of the photoreceptor 9Bk is uniformly charged by the charger 10Bk in the dark, and then exposed by the laser beam 14Bk corresponding to the black image from the exposure device 11, thereby forming an electrostatic latent image. Is done. The developing device 12Bk visualizes the electrostatic latent image with black toner, thereby forming a black toner image on the photoreceptor 9Bk.

  The toner image is transferred onto the transfer belt 5 by the primary transfer roller 15Bk at a position (primary transfer position) where the photoconductor 9Bk and the transfer belt 5 are in contact with each other. By this transfer, a toner image with black toner is formed on the transfer belt 5. When the transfer of the toner image is completed, the cleaner blade 13Bk wipes off unnecessary toner remaining on the outer peripheral surface of the photoconductor 9Bk. After the unnecessary toner is wiped off, the photoconductor 9Bk enters a standby state for the next image formation.

  As described above, the black toner image transferred to the transfer belt 5 by the AIO cartridge 6Bk is conveyed to the position of the next AIO cartridge 6M. In the AIO cartridge 6M, a magenta toner image is formed on the photoreceptor 9M by a process similar to the image forming process in the AIO cartridge 6Bk, and the toner image is superimposed on the black image formed on the transfer belt 5. Is transcribed.

  The toner image transferred onto the transfer belt 5 is further conveyed sequentially to the next AIO cartridges 6C and 6Y. By the same operation, a cyan toner image formed on the photoconductor 9C and a yellow toner image formed on the photoconductor 9Y are sequentially superimposed on the toner image transferred onto the transfer belt 5. Is transcribed. Thus, a full color image is formed on the transfer belt 5. The full-color superimposed image on the transfer belt 5 is conveyed to the position of the secondary transfer roller 16. In the case of monochrome printing with only black at the time of image formation, the primary transfer rollers 15M, 15C, and 15Y are retracted to positions separated from the photoreceptor 9M, the photoreceptor 9C, and the photoreceptor 9Y, respectively. Then, the above-described image forming process is performed only for the black color.

  Next, a paper transport operation during image formation will be described. The sheets 4 stored in the main body sheet feed tray 1 are sent out in order from the top sheet 4 when the sheet feed roller 2 is driven to rotate counterclockwise. The paper 4 sent out from the main body paper supply tray 1 stands by at the position of the registration roller 3. The registration roller 3 feeds out the paper 4 by rotating it counterclockwise at a timing when the toner image conveyed by the transfer belt 5 and the paper 4 overlap on the secondary transfer roller 16 (hereinafter, not particularly specified). As long as this secondary transfer position is referred to as a transfer portion, transfer position).

  The toner image on the transfer belt 5 is transferred to the paper 4 sent out by the registration roller 3 by the secondary transfer roller 16. The fixing device 20 fixes the toner image on the paper 4 with heat and pressure. The sheet 4 on which the toner image is fixed is discharged out of the image forming apparatus 100 by a discharge roller 18a that is driven to rotate counterclockwise.

  When paper is discharged to the duplex conveying path 219, the switchback operation is performed by rotating the paper discharge roller 18a clockwise before the trailing edge of the paper 4 passes the paper discharge sensor and passes the paper discharge roller 18a. And the sheet 4 is discharged to the duplex conveying path 219. The sheet 4 conveyed to the duplex conveyance path 219 is conveyed again to the registration roller 3 via the duplex roller 19. The sheet 4 that has reached the registration roller 3 is again fed from the registration roller 3, and the toner image is transferred to the opposite side of the sheet surface by the secondary transfer roller 16. The fixing device 20 fixes the toner image with heat and pressure. The sheet 4 on which the toner image is fixed can be discharged to the outside of the image forming apparatus 100 by a discharge roller 18a that is driven to rotate counterclockwise, and can also be discharged to the duplex conveyance path 219 again. Is possible. It is assumed that the paper discharge sensor is on the branch point of the route. Further, the fixing roller 21 is provided with a separation claw (not shown), and the separation claw enters between the paper 4 and the fixing roller 21 to prevent the paper 4 from being wrapped around the fixing roller 21. Yes.

  FIG. 2 is a schematic electrical system diagram of the image forming apparatus 100 according to the embodiment. The image forming apparatus 100 roughly includes an engine unit 101 and a controller unit 102. The engine unit 101 and the controller unit 102 are connected by a PCI bus line 103. The engine unit 101 and the controller unit 102 can communicate with each other via the PCI bus line 103. Further, the engine unit 101 and the controller unit 102 can transmit and receive image data in a sufficiently large band.

  The controller unit 102 is configured, for example, by connecting the CPU 210 and the FeROM 211 (nonvolatile ROM) to each other via the PCI bus line 103. CPU is an abbreviation for “Central Processing Unit”. PCI is an abbreviation for “Peripheral Component Interconnect”. The controller unit 102 is configured by connecting a hard disk drive 212 (HDD), a RAM 213, and a USB terminal 214 to each other via the PCI bus line 103. RAM is an abbreviation for “Random Access Memory”. USB is an abbreviation for “Universal Serial Bus”. The controller unit 102 is configured by connecting an Ethernet (registered trademark) interface 215 (Ethernet (registered trademark)) and a facsimile unit (FAX) 216 to each other via the PCI bus line 103.

  The CPU 210 executes software that controls the operation of the controller unit 102. The CPU 210 reads an image forming program stored in the FeROM 211, functions as the image data expansion unit 217, and performs image data expansion processing. The image data development processing here indicates that the image data to be transferred is ready to be output to the exposure apparatus 11 immediately. In general, the state in which image data can be immediately output to the exposure apparatus 11 often indicates that the following state is satisfied. (1) Image composition and editing have been completed. (2) The image data is decoded. (3) The image data is arranged on the RAM 204 that can be directly transferred to the exposure apparatus 11. (4) The image data is arranged on the RAM 213 that can be transferred to the exposure apparatus 11 with a sufficient transfer band.

  The FeROM 211 of the controller unit 102 stores a program such as an image forming program and various data. The CPU 210 executes the program. The HDD 212 stores the image received by the controller unit 102. The RAM 213 stores image data expanded by the CPU 210 functioning as the image data expansion unit 217. The CPU 210 freely stores data in the RAM 213 and also stores images. The RAM 213 DMA transfers image data to the engine unit 101 via the PCI bus line 103. DMA is an abbreviation for “Direct Memory Access”.

  A USB terminal (USB) 214 connects the controller unit 102 and the host computer 220 so that they can communicate with each other. The controller unit 102 receives image data from the host computer 220 via the USB terminal 214, performs image editing, image composition, and expansion processing, and generates image data that can be output. The USB terminal 214 is connected to the scanner device 221. The controller unit 102 receives image data from the scanner device 221, performs image editing, image synthesis, and expansion processing, and generates outputable image data.

  The Ethernet interface 215 is connected to a network 222 such as a LAN. LAN is an abbreviation for “Local Area Network”. The controller unit 102 receives image data supplied from a network 222 such as a LAN via the Ethernet interface 215, performs image editing, image synthesis, and expansion processing, and generates image data that can be output. The facsimile unit 216 receives a facsimile image transmitted via the telephone line 223. The controller unit 102 edits the facsimile image received by the facsimile unit 216, combines the images, and develops the generated image data.

  The engine unit 101 is configured, for example, by connecting a CPU 200, an FeROM 201, a write control unit 202, a motor driver 203, and a RAM 204 to each other via a PCI bus line 103. The CPU 200 executes a software program that controls the operation of each unit of the engine unit 101. The CPU 200 reads an image forming program stored in the FeROM 201 and functions as the image forming control unit 218, and performs image forming control of the exposure apparatus 11 and the like via the writing control unit 202.

  The FeROM 201 stores a program executed by the CPU 200 and various data. The FeROM 201 stores an image forming program executed by the CPU 200 as one of the programs. The writing control unit 202 is connected to the exposure apparatus 11. The writing control unit 202 transmits a writing signal to the exposure apparatus 11, and forms an electrostatic latent image corresponding to each color image on the photosensitive members 9Bk, 9C, 9M, and 9Y.

  The motor driver 203 freely rotates and stops the respective color photoconductors 9Bk, 9C, 9M, and 9Y and the respective motors (not shown) connected to the respective color developing devices 12Bk, 12C, 12M, and 12Y in accordance with instructions from the CPU 200. The motor driver 203 freely rotates and stops each motor (not shown) connected to the transfer belt tension roller 8, the secondary transfer driving roller 7, and the secondary transfer roller 16 in accordance with an instruction from the CPU 200. The motor driver 203 freely rotates and stops the motor (reference numeral 303 in FIG. 3) connected to the paper feed roller 2. The motor driver 203 freely rotates and stops motors (not shown) connected to the double-sided roller 19 and the paper discharge roller 18a. Further, the motor driver 203 freely changes the contact and separation between the color photoreceptors 9Bk, 9C, 9M, and 9Y and the transfer belt 5 by a cam-shaped mechanism (not shown). The CPU 200 freely stores data in the RAM 204. The CPU 200 temporarily stores image data of each color in the RAM 204. The CPU 200 reads out the image data stored in the RAM 204 and supplies the image data to the write control unit 202 at the timing of forming each color image. The writing control unit 202 controls the exposure apparatus 11 and the like so as to form an image corresponding to the image data supplied from the RAM 204.

  Here, in the image forming apparatus 100 of the embodiment, the motor driver 203 that drives the motor and the encoder sensor circuit that detects the rotational position of the motor are installed on the same circuit board and modularized ( Motor module).

  As an example, FIG. 3 shows a circuit configuration diagram of a motor module that rotationally drives the paper feed roller 2. As shown in FIG. 3, the motor module includes a low voltage source 301, a ground line 302 (GND), a motor 303, an encoder sensor circuit 304, and a current limiting resistor 305 along with the motor driver 203 described above. The motor driver 203 is an example of a first power supply unit and power supply means. The low voltage source 301 is an example of a second power supply unit and power supply means. The motor 303 is an example of a first drive unit and drive means. The encoder sensor circuit 304 is an example of a second drive unit and drive means. The current limiting resistor 305 is an example of a resistor.

  The motor driver 203 is, for example, a high voltage source of 24V. The motor driver 203 rotationally drives the motor 303 that rotationally drives the paper feed roller 2 with a voltage of 24V. The low voltage source 301 applies a voltage of 5 V, for example, to the motor driver 203. The motor driver 203 applies a voltage of 5V to the encoder sensor circuit 304 via the current limiting resistor 305 to drive the encoder sensor circuit 304. In this example, the motor driver 203 serving as a high voltage source is connected to a common ground line 302 via a motor 303, and the low voltage source 301 is connected to a common ground line 302 via a current limiting resistor 305 and an encoder sensor circuit 304. Has been. That is, the motor module is the same module with two power supplies. The motor module is inserted into and removed from the backboard (bus bar) via the connector unit 300.

  A dotted arrow shown in FIG. 3 indicates a normal current path formed when the ground line 302 is grounded (in a normal state). As indicated by the arrows in FIG. 3, a current corresponding to a high voltage of 24 V generated by the motor driver 203 serving as a high voltage source flows to the ground line 302 via the motor 303 in a normal state. Similarly, a current corresponding to a low voltage of 5 V generated by the low voltage source 301 flows to the ground line 302 via the current limiting resistor 305 and the encoder sensor circuit 304 at the normal time.

  The current limiting resistor 305 is connected in series to a line connecting the output terminal 301 a of the low voltage source 301 and the input terminal 304 a of the encoder sensor circuit 304. The current limiting resistor 305 is a resistor that prevents inconvenience that a large current flows backward into the encoder sensor circuit 304 when the motor module is inserted into and removed from the backboard (busbar) in a live state. The resistance value of the current limiting resistor 305 can prevent the current flow corresponding to the low voltage of 5V from the encoder sensor circuit 304 as much as possible and can prevent the reverse flow of the large current to the encoder sensor circuit 304. A resistance value is selected. In other words, as the resistance value of the current limiting resistor 305, a resistance value that allows the encoder sensor circuit 304 to operate normally and prevents the reverse flow of the large current to the encoder sensor circuit 304 is selected (set). .

  FIG. 4 shows a circuit diagram of the encoder sensor circuit 304. As an example, the encoder sensor circuit 304 is an incremental encoder sensor circuit that optically scans a code disk provided with a plurality of slits in an incremental track. The encoder sensor circuit 304 outputs two-phase encode outputs of A phase and B phase, which are each 90 degrees out of phase. The encoder sensor circuit 304 has a total of two pairs of photodetectors PD1 to PD4, which are a pair of first photodetector PD1 and second photodetector PD2, and a pair of third photodetector PD3 and fourth photodetector PD4. ing.

  Each photodetector PD1 to PD4 has an anode connected to the ground line 302 and is grounded. The cathodes of the photodetectors PD1 to PD4 are connected to an input terminal 304a to which a low voltage of 5 V from the low voltage source 301 is applied via a resistor R1. The detection outputs of the photodetectors PD1 to PD4 are converted into voltages by the resistor R1 and taken out. The detection output of the first photodetector PD1 is supplied via the amplifier A1 to the inverting input terminal (−) of the first comparator 351 that is a hysteresis comparator. The detection output of the second photodetector PD2 is supplied to the non-inverting input terminal (+) of the second comparator 352 that is a hysteresis comparator via the amplifier A1. The detection output of the third photodetector PD3 is supplied to the non-inverting input terminal (+) of the first comparator 351 via the amplifier A1. The detection output of the fourth photodetector PD4 is supplied to the inverting input terminal (−) of the second comparator 352 via the amplifier A1.

  The output terminal of the first comparator 351 is connected to the base of the first transistor Tr1 whose emitter is grounded. The collector of the first transistor Tr1 is connected to an input terminal 304a to which a low voltage of 5V from the low voltage source 301 is applied via a resistor rd1 for taking out the output as a voltage value. A first output terminal 361 is connected between the collector of the first transistor Tr1 and the resistor rd1. An a-phase encoded output is taken out via the first output terminal 361.

  The output terminal of the second comparator 352 is connected to the base of the second transistor Tr2 whose emitter is grounded. The collector of the second transistor Tr2 is connected to an input terminal 304a to which a low voltage of 5V from the low voltage source 301 is applied via a resistor rd2 for extracting the output as a voltage value. A second output terminal 362 is connected between the collector of the second transistor Tr2 and the resistor rd2. The b-phase encoded output is taken out via the second output terminal 362.

  FIG. 5 is a diagram showing the relationship between each of the photodetectors PD1 to PD4 and the slit 371 of the code disk 370. As shown in FIG. The code disk 370 is provided with a plurality of slits 371 that move according to the rotation of the motor 303. The size of each slit 371 is such that two of the photodetectors PD1 to PD4 arranged in parallel at equal intervals along the moving direction of the slit 371 can be looked into. That is, the size of each slit 371 is slightly larger than the size when the two photodetectors are arranged. Also, the interval between the slits 371 is slightly larger than the size when two photodetectors are arranged as shown by the dotted line in FIG. For this reason, as shown in FIG. 5, when the first slit 371 moves to a position where the first and second photodetectors PD1 and PD2 can be seen, the third and fourth photodetectors PD3 are moved. PD4 is shielded by a portion other than the slit 371. That is, in this case, the third and fourth photodetectors PD3 and PD4 are shielded by a portion between adjacent slits 371 of the code disk 370.

  In such an encoder sensor circuit 304, the light emitted from the light emitting diode led 1 shown in FIG. 4 is converted into parallel light through a parallel lens and irradiated onto the code disk 370. Each of the photodetectors PD1 to PD4 receives the light emitted from the light emitting diode led1 through the slit 371 of the code disk 370 that moves according to the rotation of the motor 303, and forms a detection output corresponding to the amount of light. The first comparator 351 which is a hysteresis comparator to prevent the influence of noise is a first transistor with a rectangular wave corresponding to the difference between the detection outputs of the first photodetector PD1 and the third photodetector PD3. The tr1 is turned on / off. As a result, an a-phase encoded output corresponding to the difference between the detection outputs of the first photodetector PD1 and the third photodetector PD3 is output via the first output terminal 361. The second comparator 352, which is a hysteresis comparator for preventing the influence of noise, is a second rectangular wave corresponding to the difference between the detection outputs of the second photodetector PD2 and the fourth photodetector PD4. The transistor tr2 is turned on / off. As a result, the b-phase encoded output corresponding to the difference between the detection outputs of the second photodetector PD2 and the fourth photodetector PD4 is output via the second output terminal 362.

  FIG. 6 is a diagram illustrating a two-phase encoding output of the A phase and the B phase output from the encoder sensor circuit 304 provided in the image forming apparatus of the embodiment. FIG. 6 shows the A-phase and B-phase encoding outputs output from the encoder sensor circuit 304 when the code disk 370 moves in the direction indicated by the arrow in FIG. In this case, the A-phase encode output is formed first, and the B-phase encode output is formed with a phase difference of 90 degrees with a delay. When the code disk 370 is moved in the direction opposite to the arrow in FIG. 5, the B-phase encoded output is formed first, and the A-phase encoded output is formed with a 90 degree phase difference. The The encoded output of each phase is processed by an encoder counter (not shown) and compared with a rotation control signal of the motor 303 from the CPU 200 shown in FIG. 2 in a comparator (not shown). The motor driver 203 shown in FIG. 3 rotates the motor 303 according to the difference between the count output from the encoder counter and the rotation control signal from the CPU 200 (closed loop). Thereby, the rotation direction, rotation speed, and rotation position of the motor 303 can be accurately controlled.

  FIG. 7 shows a circuit configuration diagram of a motor module as a comparative example. The motor module shown in FIG. 3 is provided with the current limiting resistor 305, but the motor module according to the comparative example shown in FIG. 7 is not provided with the current limiting resistor 305. Other configurations are the same for both. That is, also in the motor module of the comparative example shown in FIG. 7, the motor driver 401 and the low voltage source 402 serving as the high voltage source are connected to the common ground line 405 and grounded. The motor driver 401 drives the motor 403 with a high voltage of 24V. The encoder sensor circuit 404 is driven with a low voltage from a low voltage source 402 of 5V.

  In such a motor module as a comparative example, let us consider a case where the ground line 405 is not grounded and is inserted into and removed from the backboard in a live state (at the time of hot insertion / extraction). In this case, a large current corresponding to a voltage of 24 V from the motor driver 401 flows back into the encoder sensor circuit 404 via the motor 403 and the ground line 405. 7 indicates a current path of a large current corresponding to a voltage of 24 V, and the thickness of the arrow indicates the amount of current. In the motor module as a comparative example, a potential difference of 19 V is generated in the encoder sensor circuit 404 due to the reverse flow of the above-described current, and the encoder sensor circuit 404 is damaged.

  FIG. 8 shows a current path and a current amount when the motor module provided in the image forming apparatus 100 of the embodiment is hot-plugged. In FIG. 8, the direction indicated by the dotted arrow indicates the direction in which the current flows. In FIG. 8, the thickness of the arrow indicates the amount of current. As can be seen from FIG. 8, when the hot insertion / extraction of the motor module of the embodiment is performed, a large amount of current corresponding to the voltage of 24 V from the motor driver 203 is encoded via the motor 303 and the ground line 302. An attempt is made to reversely flow into the sensor circuit 304.

  However, when the current flows backward into the encoder sensor circuit 304, the current limiting resistor 305 functions effectively, and the current amount (flow amount) of the current that is going to flow backward into the encoder sensor circuit 304 is greatly reduced. The thickness of the arrow in FIG. 8 indicates the difference between the current amount before reduction and the current amount after reduction. As can be seen from FIG. 8, it can be seen that the amount of current flowing back into the encoder sensor circuit 304 is greatly reduced by the function of the current limiting resistor 305. As a result, it is possible to prevent the encoder sensor circuit 304 from being damaged due to a large current from the motor driver 203 flowing back into the encoder sensor circuit 304 when the motor module is hot-plugged.

  As is clear from the above description, the image forming apparatus 100 according to the embodiment connects the motor driver 203 as an example of the high voltage source to the ground line 302 via the motor 303. In the image forming apparatus 100 according to the embodiment, the low voltage source 301 is connected to the ground line 302 via the encoder sensor circuit 304. A current limiting resistor 305 is connected in series to a line connecting the output terminal 301a of the low voltage source 301 and the input terminal 304a of the encoder sensor circuit 304 to form a motor module. As a result, the amount of current that flows back into the encoder sensor circuit 304 from the motor driver 203 via the ground line 302 when the motor module is hot-plugged can be greatly reduced. For this reason, the inconvenience that the encoder sensor circuit 304 is damaged by the reversely flowing current can be prevented.

  In addition, the image forming apparatus 100 according to the embodiment has a resistance value that allows the encoder sensor circuit 304 to operate normally as the current limiting resistor 305 and prevents the above-described large current from flowing back into the encoder sensor circuit 304. A limiting resistor 305 is provided. Therefore, even when the ground line 302 is grounded and the motor module is normally operated, the encoder sensor circuit 304 can be normally operated with a low voltage of 5 V from the low voltage source 301. That is, in the image forming apparatus 100 according to the embodiment, the operation of the encoder sensor circuit 304 is not hindered by providing the current limiting resistor 305.

  It is also conceivable to form a voltage dividing circuit using a Zener diode, and to prevent the above-described reverse inflow when the motor module is hot-plugged. However, since the Zener diode is an expensive component, if a voltage dividing adjustment circuit formed using the Zener diode is provided on each of a large number of modular circuit boards, the cost of the entire device increases. On the other hand, in the case of the image forming apparatus 100 according to the embodiment, an inexpensive resistor (current limiter) is provided between the low voltage source 301 and the drive target circuit of the low voltage source 301 (encoder sensor circuit 304 in this example). The effect described above can be obtained simply by connecting the resistors 305) in series. For this reason, even if the current limiting resistor 305 is provided on a large number of modular circuit boards, the cost of the image forming apparatus 100 is hardly affected. For this reason, the safe image forming apparatus 100 that can prevent the reverse flow of the current described above and prevent the circuit from being damaged can be realized at low cost.

  Next, some modified examples of the image forming apparatus according to the embodiment will be described. In the above description of the embodiment, the encoder sensor circuit 304 is an incremental encoder sensor circuit that outputs a two-phase encoded output. Instead, an incremental encoder sensor circuit that outputs a one-phase encoded output may be provided.

  FIG. 9 is a circuit diagram of an incremental encoder sensor circuit 500 that outputs a one-phase encoded output. The encoder sensor circuit 500 includes a first photo detector PD1 and a second photo detector PD2 that form a pair. Each of the photodetectors PD1 and PD2 is connected to the ground line 302 and grounded. The cathodes of the photodetectors PD1 and PD2 are connected to an input terminal 304a to which a low voltage of 5 V from the low voltage source 301 is applied via a resistor R1.

  The detection outputs of the photodetectors PD1 and PD2 are converted into voltages by the resistor R1 and taken out. The detection output of the first photodetector PD1 is supplied to the inverting input terminal (−) of the comparator 501 serving as a hysteresis comparator via the amplifier A1. The detection output of the second photodetector PD2 is supplied to the non-inverting input terminal (+) of the comparator 501 via the amplifier A1.

  The output terminal of the comparator 501 is connected to the base of the transistor Tr whose emitter is grounded. The collector of the transistor Tr is connected to an input terminal 304a to which a low voltage of 5V from the low voltage source 301 is applied via a resistor rd for extracting the output as a voltage value. An output terminal 502 is connected between the collector of the transistor Tr and the resistor rd. One-phase encoded output is taken out via the output terminal 502.

  In such an encoder sensor circuit 500, the light emitted from the light emitting diode led is converted into parallel light through a parallel lens and irradiated onto the code disk 370 (see FIG. 5). Each of the photodetectors PD1 and PD2 receives the light emitted from the light emitting diode led through the slit 371 of the code disk 370 that moves according to the rotation of the motor 303, and forms a detection output corresponding to the amount of light. A comparator 501 serving as a hysteresis comparator in order to prevent the influence of noise causes the transistor tr to be turned on and off with a rectangular wave corresponding to the difference between the detection outputs of the first photodetector PD1 and the second photodetector PD2.

  As a result, one-phase encoded output (A-phase or B-phase encoded output shown in FIG. 6) corresponding to the difference between the detection outputs of the first photodetector PD1 and the second photodetector PD2 is output via the output terminal 502. Is done. Even when such a one-phase encoder sensor circuit 500 is provided instead of the two-phase encoder sensor circuit 304, the reverse flow of the current to the encoder sensor circuit 500 can be greatly reduced, and the above-described implementation is performed. The same effect as the embodiment can be obtained.

  As another modification of the image forming apparatus 100 of the embodiment, an FG (Frequency Generator) sensor may be provided instead of the encoder sensor circuit 304. The FG sensor has, on the rotor side, a ring-shaped magnet that is subjected to NS multipolar magnetization in the circumferential direction separately from the magnetization for driving the motor. The FG sensor has an FG pattern on the stator side in which the same number of wire elements as the number of magnetized magnetic poles are connected in series in the circumferential direction. The FG sensor outputs a speed detection signal (FG signal) generated from the FG pattern by the rotation of the rotor and having a frequency proportional to the rotational speed of the rotor. Even when such an FG sensor is provided instead of the two-phase encoder sensor circuit 304, the reverse flow of the current to the FG sensor can be greatly reduced, and the same effect as the above-described embodiment can be obtained. be able to.

  As still another modification of the image forming apparatus 100 of the embodiment, a hall element sensor 600 may be provided as shown in FIG. 10 instead of the encoder sensor circuit 304. In this case, the rotor 601 of the motor 303 is alternately magnetized to the S pole and the N pole along the circumferential direction. As an example of the hall element sensor 600, an alternating detection type hall element sensor is provided. The Hall element sensor 600 performs an on / off operation in accordance with magnetic fields of S and N poles that are alternately applied as the rotor 601 rotates. The hall element sensor 600 outputs an encoded output with a period corresponding to the rotation speed of the motor 303. Even when such a Hall element sensor 600 is provided in place of the two-phase encoder sensor circuit 304, the reverse inflow of the current to the Hall element sensor 600 can be greatly reduced. The same effect can be obtained.

  The above-described embodiments are presented as examples, and are not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. For example, the circuit driven by the low voltage source 301 may be a circuit other than the encoder sensor circuit 304. Even when other circuits are provided, by connecting the current limiting resistor 305 in series between the low voltage source 301 and the other circuits, the reverse flow of the current to the other circuits can be greatly reduced. The same effects as those of the above-described embodiment can be obtained. In addition, a module (motor module) having a total of two power supply units, that is, a motor driver 203 and a low voltage source 301 as an example of a high voltage source has been described. This may be a module having one high voltage source and two low voltage sources, or a module having two high voltage sources and one low voltage source. That is, a module having one or more high voltage sources and one or more low voltage sources, and having a current limiting resistor 305 connected in series between the low voltage source and a circuit driven by the low voltage source By doing so, the same effect as described above can be obtained. When a high voltage source, a medium voltage source, and a low voltage source are provided, a current limiting resistor 305 is connected in series between the low voltage source and a circuit driven by the low voltage source, and the medium voltage source and the medium voltage source are connected. A current limiting resistor 305 is preferably connected in series with a circuit driven by a voltage source. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1 Main body paper feed tray 2 Paper feed roller 3 Registration roller 4 Paper 5 Transfer belt 6Bk AIO cartridge (Black)
6M AIO cartridge (magenta)
6C AIO cartridge (cyan)
6Y AIO cartridge (yellow)
7 Secondary transfer driving roller 8 Transfer belt tension roller 9Bk Photoconductor (Black)
9M photoconductor (magenta)
9C photoconductor (cyan)
9Y photoconductor (yellow)
10Bk charger (black)
10M charger (magenta)
10C charger (cyan)
10Y charger (yellow)
11 Exposure equipment 11Bk Exposure equipment (Black)
11M exposure system (magenta)
11C exposure equipment (cyan)
11Y Exposure system (yellow)
12Bk Developer (Black)
12M Developer (Magenta)
12C Developer (Cyan)
12Y Developer (Yellow)
13Bk Cleaner Blade (Black)
13M Cleaner blade (magenta)
13C Cleaner blade (Cyan)
13Y Cleaner Blade (Yellow)
14Bk laser light (black)
14M laser light (magenta)
14C laser light (cyan)
14Y Laser light (yellow)
15Bk primary transfer roller (black)
15M primary transfer roller (magenta)
15C primary transfer roller (cyan)
15Y primary transfer roller (yellow)
16 Secondary transfer roller 18a Paper discharge roller 19 Double-sided roller 20 Fixing device 21 Fixing roller 100 Image forming apparatus 101 Engine unit 102 Controller unit 103 PCI bus line 200 CPU
201 Nonvolatile ROM (FeROM)
202 Write control unit 203 Motor driver (high voltage source: 24V)
204 RAM
210 CPU
211 Nonvolatile ROM (FeROM)
212 Hard disk drive (HDD)
213 RAM
214 USB terminal 215 Ethernet interface 216 Facsimile unit 217 Image data development unit 218 Image creation control unit 219 Double-sided conveyance path 220 Host computer 221 Scanner device 222 Network 223 Telephone line 300 Motor module connector unit 301 Low voltage source (5 V)
301a Output terminal of low voltage source 302 Ground line (GND)
303 Motor 304 Two-phase output encoder sensor circuit 304a Encoder sensor circuit input terminal 305 Current limiting resistor 351 First comparator 352 Second comparator 361 First output terminal 362 Second output terminal 370 Code disk 371 Code Disc slit 401 Motor driver (High voltage source: 24V)
402 Low voltage source (5V)
403 Motor 404 Encoder sensor circuit 405 Ground line (GND)
500 1-phase output encoder sensor circuit 501 comparator 502 output terminal 600 Hall element sensor 601 motor rotor PD1 first photo detector PD2 second photo detector PD3 third photo detector PD4 fourth photo detector LED light emitting diode LED1 light emitting diode R1 resistance A1 amplifier Tr transistor Tr1 first transistor Tr2 second transistor RD resistor RD1 resistor RD2 resistor

JP-A-6-168863

Claims (8)

Power supply means comprising at least a first power supply unit and a second power supply unit that supplies a lower voltage than the first power supply unit;
Drive means comprising at least a first drive unit driven by a voltage from the first power supply unit and a second drive unit driven by a voltage from the second power supply unit;
A ground line for commonly grounding each of the drive units of the drive means;
An electronic device comprising: a resistor connected in series to a line connecting the second power supply unit and the second drive unit. The power supply means, the drive means, the ground line, and the resistor are modularized,
The electronic device according to claim 1, further comprising a connector portion for connecting the module to a bus. The resistor operates a current amount of a current corresponding to a voltage of the first power supply unit that normally operates the second drive unit and flows back into the second drive unit via the ground line. The electronic device according to claim 1, wherein the resistance value is set to be reduced. A motor as the first drive unit;
The electronic device according to claim 1, further comprising: a motor driver that supplies a voltage to the motor as the first power supply unit. The second drive unit includes an encoder sensor circuit that outputs a two-phase encoded output, an encoder sensor circuit that outputs a one-phase encoded output, an FG (Frequency Generator) sensor, or a Hall element sensor. The electronic device according to any one of claims 1 to 4. A high voltage source that generates a high voltage to drive the motor;
A low voltage source for generating a low voltage lower than the high voltage;
An encoder sensor circuit that is driven at the low voltage and outputs an encode output corresponding to the rotation of the motor;
A ground line for common grounding the motor and the encoder sensor circuit;
A resistor connected in series to a line connecting the low voltage source and the encoder sensor circuit;
A connector portion for connecting the high voltage source, the low voltage source, the encoder sensor circuit, and the ground line to a bus;
The motor driving device according to claim 1, wherein the high voltage source, the low voltage source, the encoder sensor circuit, the ground line, and the connector portion are modularized and inserted into and removed from a bus bar through the connector portion. The resistor is set to a resistance value that causes the encoder sensor circuit to operate normally and reduces the amount of current corresponding to the high voltage that flows back into the encoder sensor circuit via the ground line. The motor drive device according to claim 6.   An image forming apparatus comprising the motor drive device according to claim 6.

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